The present invention relates to biometrics, and more specifically, to electronic verification and identification of individuals using biometrics.
Securing computer systems and electronic transactions is becoming more and more important as we enter the electronic age. Existing password and cryptographic techniques seem well on their way to solving the security problems of computer systems, electronic commerce, and electronic transactions. These solutions ensure that the set of digital identification keys associated with an individual person can safely carry on electronic transactions and information exchanges. Little, however, has been done to ensure that such identification keys can only be used by their legitimate owners. This is a critical link that needs to be made secure if secure computer access, electronic commerce, home banking, point of sale, electronic transactions, and similar mechanisms are to become truly secure.
Today, passwords handle most of these issues. For example, most electronic transactions, such as logging into computer systems, getting money out of automatic teller machines, processing debit cards, electronic banking, and similar transactions require passwords. Passwords are an imperfect solution because as more and more systems attempt to become secure, a user is required to memorize an ever expanding list of passwords. Additionally, passwords are relatively easily obtained by observing an individual when he or she is entering the password. Moreover, there is no guarantee that users will not communicate passwords to one another, lose passwords, or have them stolen. Thus, passwords are not considered sufficiently secure for many functions.
More and more often, fingerprint identification is considered. Fingerprints have the advantage of being unique to an individual person, requiring no memorization, and being relatively difficult to appropriate. Thus, some secure systems are switching to fingerprint recognition. Fingerprint recognition generally requires a user to place his or her finger on a fingerprint sensing device. Each fingerprint consists of a unique arrangement of ridges and grooves. The fingerprint sensing device transmits an analog image of the user""s fingerprint, via a coaxial cable, to a computer system. The computer system then matches the fingerprint to a database of fingerprint templates in the computer system. However, there are a number of problems with prior art fingerprint identification methods.
First, the fingerprint sensing devices, the devices on which the finger is placed, are generally bulky. This means that such devices can not be adapted to be used with portable computers, consumer electronics, or in situations where space is precious.
Additionally, fingerprint devices generally require a connection to a power outlet in addition to the connection to the computer system. This means that if the fingerprint device needs to be used, an additional power outlet is consumed. Thus, such devices can not be adapted for use in situations where extra power outlets are not available.
Furthermore, because conventional fingerprint devices generally transmit an analog image of the fingerprint, via a coaxial cable, security may be breached. The analog fingerprint image may be obtained by intercepting the image transmitted on the coaxial cable. Thus, if a false user had an image capturing device, he or she may be able to impersonate an original user, by resending a captured image. This reduces security in cases where the actual fingerprint sensing procedure is not observed by anyone.
Furthermore, because fingerprint processing in conventional systems generally takes place in the computer system, the computer system itself can be corrupted to defeat the security provided by the fingerprint sensing device. In the end, the computer system decides whether the fingerprint received from the device matches a print in the database. Either the database can be altered or the process which matches the print to the database can be altered to send a false positive indication. In this way, the advantages of the fingerprint sensing system may be lost.
Moreover, in conventional systems the user is required to interact with the fingerprint sensing system. Generally, the prior art process of sensing a fingerprint is as follows. First, the user positions his or her finger on the sensing sensor platen. An image of the fingerprint is displayed on the computer monitor, with a cross-hair. The user is asked to position his or her finger such that the cross hairs are centered, and that the print is clearly displayed. When the user has determined that the finger is in the proper position, the user must press a button to indicate that this is the image to be transmitted. Once the user has selected the proper fingerprint, the device takes an image, and sends it to the computer system for processing. However, this awkward and error-prone procedure requires active participation and control by the user. It would be advantageous if such interaction were not required.
In addition, the conventional fingerprint devices are not very accurate if the user""s finger is too dry or oily, or if the sensor platen on which the finger is placed is dirty. This occurs for a number of reasons. Generally conventional fingerprint devices take a picture of the finger which was placed on the sensor platen. Places where there is something contacting the sensor platen, such as a ridge on a finger, do not reflect the light, but rather absorb it. Places where there is nothing contacting the sensor platen, such as grooves in the fingerprint, reflect the light. This produces an image of absorbed and reflected light on the sensing sensor platen. However, dirt and smudges on the sensor platen can also absorb light thereby producing a false image. This image represents all of the dirt and smudges on the sensor platen, in addition to showing the actual fingerprint. One method of solving this, in the prior art, is to shine a stronger light on the finger as the image is captured. The stronger light is strong enough to break through smudges on the sensor platen, and thus light is reflected even if there is some residue on the sensor platen. However, using such a stronger light causes other problems. The brighter light also requires more power. The brighter light is also less likely to pick up on fingerprints which are not perfectly clear. If, for example, the user""s finger is dry, the ridges are not well defined, and the brighter tight may not pick them up.
Thus, a more accurate fingerprint sensing method is needed, which is not adversely impacted by a dirty sensor platen, and which does not allow the security breaches of the prior art.
The method and apparatus for fingerprint recognition is provided. A fingerprint is detected on a sensor. The fingerprint is digitized. A digitized background is subtracted from the fingerprint, resulting in a difference print. The difference print is matched with a database of fingerprint templates.
The background is obtained by taking an image of the sensor platen at the time of startup, and after each fingerprint is detected. Thus, the current state of the background, including smudges, lighting unevenness, and other factors are detected and subtracted from the digitized fingerprint.